Nanophotonic Global Shutter Pixel Layout for Parasitic Light Isolation
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Solution Overview
Problem
Global shutter imaging systems with back-side illumination sensors face challenges in protecting charge storage nodes from unwanted charge, particularly parasitic light, due to the difficulty in isolating these nodes from the back-side of photodiode substrates.
Innovation Solution
The implementation of nanophotonic light guides, or spectral routers, positioned on the front-side of the image sensor pixels, diverts unwanted photons away from the charge storage nodes, improving light collection while preventing unwanted charge accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If back-side illumination sensors are used to improve light collection capability, then light sensitivity is improved, but charge storage nodes become vulnerable to unwanted charge from reflected and scattered light
Solution Approach 1:
A spectral router is introduced as an intermediary component between the back-side illumination interface and the charge storage node. The spectral router selectively routes different wavelengths of light: directing desired wavelengths to the photosensitive region while diverting unwanted reflected and scattered light away from the charge storage node, thus mediating between the beneficial and harmful effects of back-side illumination
Solution Approach 2:
The solution applies different optical path treatments to different regions of the sensor. The spectral router creates locally optimized light paths where the photosensitive region receives full illumination while the charge storage node region is protected from unwanted light, achieving local quality differentiation to resolve the contradiction
2Object-affected harmful factors
If charge storage nodes are positioned on the front-side of photodiode substrates to protect from unwanted light, then protection from parasitic light is improved, but back-side illumination capability is lost
Solution Approach 1:
The patent resolves the spatial conflict by adding an optical dimension through the spectral router. Instead of changing the physical position of the charge storage node, the solution uses wavelength-selective routing to create virtual spatial separation, allowing the node to remain in its optimal position while achieving protection through dimensional differentiation in the optical domain
3Object-affected harmful factors
If deep trench isolation is extended toward the charge storage node to block unwanted light, then isolation effectiveness is improved, but light collection efficiency decreases
Solution Approach 1:
The spectral router acts as an intermediary that replaces the need for extensive deep trench isolation. By routing unwanted light away before it reaches the charge storage node, the spectral router eliminates the trade-off between isolation effectiveness and light collection efficiency that would otherwise require compromising the deep trench isolation design
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively reduces the impact of parasitic light on charge storage nodes, enhancing the overall light collection capability and reducing unwanted charge collection, thereby improving the performance of back-side illumination image sensor pixels.
Implementation Method 1
The spectral router is configured to route photons of a first wavelength received at the spectral router into the photosensitive region and away from the charge storage node. The spectral router is also configured to route photons of a second wavelength received at the spectral router to one or more neighboring image sensor pixels.
Data Source
AI summary
Image sensor pixels, imaging systems, and methods for constructing image sensor pixels. The image sensor pixel includes a photosensitive region, a charge storage node, a deep trench isolation, and a spectral router. The charge storage node is positioned on a back-side of the photosensitive region. The deep trench isolation extends from a front-side of the photosensitive region toward the charge storage node. The spectral router is positioned on the front-side of the photosensitive region. The spectral router is configured to route photons of a first wavelength received at the spectral router into the photosensitive region and away from the charge storage node. The spectral router is also configured to route photons of a second wavelength received at the spectral router to one or more neighboring image sensor pixels.